1. Field of the Invention
This invention relates to a composite type magnetic head of novel construction for use in a magnetic recording and replaying device such as a hard disc drive, and more particularly to a composite type magnetic head which is constructed to preclude a pseudo-gap and to be as capable of high-density recording and replaying of information as a thin film head, yet can be easily manufactured.
2. Description of the Prior Art
In recent years, in the field of magnetic recording devices, the so-called metal type recording media using a magnetic powder of high coercive force have been finding utility in such magnetic recording media as hard discs to meet the demand for further densification of recording signals.
The trend of such recording media toward adoption of increasingly high coercive force has necesitated enhancement of the intensity of the magnetic field to be formed in the magnetic gap on the side of the magnetic head performing the operation of magnetic recording and replaying. A MIG (metal-in-gap) head so constructed as to have a metal magnetic film of high saturation flux density disposed in the proximity of the magnetic gap has found acceptance for actual use.
As an example of the MIG head, the composite type MIG head produced by a process which comprises depositing such a metal magnetic film as a Fe-Al-Si alloy film by the vacuum deposition method or the spattering method on the surface forming at least one magnetic gap in a pair of magnetic head cores made of such an oxide magnetic material as Ni-Zn ferrite or Mn-Zn ferrite, fitting fast inside the end part groove of a non-magnetic slider a magnetic head core chip having the pair of core pieces integrally joined with a glass member, fusing the inserted magnetic head core chip with glass having a lower melting point than the glass used during the formation of the magnetic gap, and thereafter winding an electromagnetic transducer coil around the magnetic head cores has been known to the art.
Besides, the so-called monolithic type MIG head so constructed that a metal magnetic film is deposited on one of a pair of magnetic head cores of an oxide magnetic material and adapted to serve concurrently as a slider is simple in design and easy to manufacture.
The surface of deposition between the magnetic head core of oxide magnetic material and the metal magnetic film is prone to occurrence of a pseudo-gap due to the deterioration of the metal magnetic film during the initial stage of film formation or the fabrication strain remaining the magnetic head cores of oxide magnetic material. This pseudo-gap possibly gives birth to swells in the frequency characteristic of the replay output.
As a magnetic head promising to meet the demand for the densification of recording signals, the film head is expected to constitute the mainstream of high-density magnetic heads yet to be introduced in the future.
The film head has a construction such that magnetic cores (magnetic poles) and an electromagnetic transducer coil are formed and laid out with high accuracy on a substrate by the so-called photolithographic technique such as spattering etching, ion etching, or chemical etching during the course of manufacture.
The film head of this construction generally has a lower protective film, a lower magnetic pole, a gap insulating layer, a photoresist, an electromagnetic transducer coil, a photoresist, an upper magnetic pole, and an upper protective film sequentially superposed in the order mentioned accurately on a non-magnetic ceramic substrate by the aforementioned photolithographic technique.
The vertical film head, in the same construction as described above, has an electromagnetic transducer coil and a main magnetic pole formed by the aforementioned photolithographic technique on a magnetic substrate made of such an oxide magnetic material as Ni-Zn ferrite or Mn-Zn ferrite in such a manner that the magnetic substrate will function as another magnetic pole, i.e., an auxiliary magnetic pole.
Since the film head is manufactured by a procedure based on the semiconductor production technology as described in detail above, the magnetic cores (magnetic poles) and the electromagnetic transducer coil can be formed with high accuracy. It, therefore, possesses outstanding characteristics as a magnetic head particularly fit for the trend toward high-density recording.
The film head, however, has a complicated construction as compared with the aforementioned MIG head. The procedure for its manufacture, therefore, is complicated and diversified. The film head has a disadvantage that it is produced in poor yield and is expensive.
The electromagnetic transducer coil which is formed by the photolithographic technique generally has a thickness of about 2 .mu.m and, therefore, finds limited room for improvement in the efficiency of electromagnetic transduction.